JP3271322B2 - Treatment of wastewater containing dimethyl sulfoxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating wastewater containing dimethyl sulfoxide (DMSO), and more particularly to a method for treating wastewater containing DMS.
DMS for efficient biological treatment of O-containing wastewater at low cost
The present invention relates to a method for treating O-containing wastewater.

[0002]

2. Description of the Related Art In recent years, a detergent containing DMSO has been used in the field of liquid crystal panel manufacturing and semiconductor manufacturing. DM
SO can be biodegraded by using acclimated bacteria, and can basically be treated with activated sludge.

In recent years, DMSO has been widely used in a semiconductor manufacturing process and a liquid crystal panel manufacturing process.
The treatment method of SO-containing wastewater is important, but when these DMSO-containing wastewaters are treated by a general activated sludge treatment, methyl sulfide (DMS) is one of the metabolites generated during the biodegradation of DMSO. And methyl mercaptan (MM) remains, and odor is generated from the aeration tank and the treated water. For this reason, conventionally, it has been considered that it is difficult to treat the activated sludge of the DMSO-containing wastewater, and at present, the treatment of the DMSO-containing wastewater is incinerated or oxidized by an oxidizing agent.

[0004]

However, incineration requires a fuel and a neutralizing agent, and oxidizing requires an oxidizing agent and a coagulant, all of which have high processing costs.

[0005] For this reason, there is a demand for a method for industrially treating wastewater containing DMSO by biological treatment capable of reducing the maintenance cost, but as described above, a treatment system based on the activated sludge treatment system is required. Then, efficient operation with an increased load leads to an increase in the generation of odor, and a large-scale deodorizing facility is required. Therefore, there is a demand for the development of a biological treatment system in which the generation amount of odor is small, the treatment efficiency is high, and the treatment device is compact.

The present invention has been made in view of the above-mentioned conventional circumstances, and solves the problem of odor generation when treating DMSO-containing wastewater by biological treatment, and treats wastewater with high treatment efficiency at low cost. It is an object of the present invention to provide a method for treating wastewater containing DMSO.

[0007]

According to the method for treating wastewater containing DMSO of the present invention, the wastewater containing dimethylsulfoxide is treated as follows.
After mixing with wastewater containing an organic substance other than dimethyl sulfoxide, and after performing the anaerobic treatment on the mixed wastewater in an anaerobic treatment tank,
Aerobic treatment in an aerobic treatment tank in which aeration is performed, and then a method of obtaining treated water by solid-liquid separation treatment, wherein at least a part of the sludge separated by the solid-liquid separation treatment,
The sludge is returned to the anaerobic treatment tank and the aerobic treatment tank as returned sludge.

[0008]

The biodegradation of DMSO is as shown in FIG.
Via S, MM and finally to sulfate ion, or
From DMS to carbon dioxide via aldehyde and formic acid,
It is generally known that it is decomposed.

In the study of the present inventors, the use of activated sludge from a municipal sewage treatment plant or a human waste treatment plant has been
Could be decomposed to sulfate ions via DMS, MM, and H ₂ S (hydrogen sulfide). Thus, as a result of a detailed examination of these decomposition routes, the decomposition of DMSO to DMS is close to a reduction reaction, while the decomposition after DMS is oxidative decomposition. It was expected that efficient treatment would be possible by combining with the oxidation reaction.

The characteristics of the biodegradation of DMSO obtained from the study results in the present invention will be described below in detail.

Decomposition of DMSO to DMS Biodegradation of DMSO to DMS is difficult to perform with DMSO alone, but by mixing an organic substance having good biodegradability, such as glucose and ethanol, with DMSO, the decomposition under aerobic conditions is achieved. Under anaerobic conditions, about 1.7 times higher decomposition rate was obtained. In an anaerobic decomposition reaction, other organic substances mixed with DMSO serve as a source of hydrogen,
It is expected that the reduction reaction from to DMS proceeded quickly (see FIG. 3).

Decomposition of DMS into MM, H ₂ S, and sulfate ions The decomposition of DMS into sulfate ions via MM and H ₂ S proceeds under aerobic conditions. At this time, organic substances other than DMS are mixed. However, the decomposition rate did not increase (see FIG. 4).

Accordingly, as a method for biodegrading DMSO, an organic substance having good biodegradability is mixed with DMSO wastewater,
First, DMSO is decomposed into DMS by performing an anaerobic treatment, and then aerobic treatment is performed, and DM generated by the anaerobic treatment is performed.
By decomposing S to sulfate ions, DMSO can be treated efficiently.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment of a method for treating wastewater containing DMSO of the present invention.

In the figure, 1 is an anaerobic treatment tank provided with a stirrer 1A, 2 is an aerobic treatment tank provided with an aeration tube 2A, 3 is a sedimentation tank, and 4 is a biological deodorizer.

In the method of the present embodiment, DMSO-containing wastewater is supplied from a pipe 11 and organic matter-containing water other than DMSO is supplied from a pipe 12 to the anaerobic treatment tank 1. Mix and perform anaerobic treatment.

Here, the DM mixed with the DMSO-containing wastewater is
Organic substances other than SO include organic substances such as sugars, alcohols and amines having good biodegradability, and generally BOD and COD.
It is preferable that the ratio of BOD / CODcr to cr is 0.5 or more (specifically, washing wastewater containing isopropyl alcohol or ethanol).
It is preferable that the concentration be 10% or more based on the reduced concentration. That is, when the mixing ratio of the organic matter is small, the decomposition rate of DMSO to DMS under anaerobic conditions may be reduced.
It is preferably set to 100%.

In the anaerobic treatment tank 1, the DMSO in the DMSO-containing wastewater mixed with organic matter is decomposed into DMS in the tank under anaerobic conditions without supplying oxygen (air). .

In the anaerobic treatment tank 1, the pH of the liquid in the tank is adjusted within a range of 6.0 to 7.5, and the liquid temperature is adjusted to 20 to 7.5.
Preferably, the temperature is adjusted to 35 ° C. In addition, the stirrer 1
The raw water and the sludge are sufficiently mixed by performing gentle stirring with A.

The load of the anaerobic treatment tank 1 is the sludge DM.
Although it varies depending on the SO decomposition capacity, sludge concentration, and the degree of biodegradability of the organic matter added to and mixed with the wastewater containing DMSO, the TOC load per day for a tank capacity of 1 m ^{3 is} 2.0%.
It is appropriate that the pressure be not more than kg-TOC / m ³ · day.

The gas generated by the anaerobic treatment in the anaerobic treatment tank 1 contains D generated by the decomposition of DMSO.
Since anaerobic treatment tank 1 contains MS, the anaerobic treatment tank 1 has a completely sealed structure, and all generated gas is sucked from piping 13 and guided to biological deodorizing device 4 to perform deodorizing treatment.

The gas generated in the anaerobic treatment tank 1 is as follows:
It may be blown into the aerobic treatment tank 2 described later.

The effluent of the anaerobic treatment tank 1 in which DMSO has been decomposed into DMS by anaerobic treatment in the presence of organic matter is then transferred from the pipe 14 to the aerobic treatment tank 2,
Performs oxidative decomposition after DMS. This aerobic treatment tank 2
Is generally a complete mixing system for an activated sludge treatment apparatus, but may be a contact aeration system in which a filler is provided inside a tank. This aerobic treatment tank may be a single tank, or a plurality of aerobic treatment tanks connected in series.

Although the load of the aerobic treatment tank depends on the performance of the anaerobic treatment tank in the preceding stage, the TOC concentration of the raw water per day per 1 m ³ of the tank is 1.0 kg-TOC / m ³ · d.
ay or less is appropriate.

It is preferable that the pH and the temperature of the liquid in the aerobic treatment tank are adjusted in the same range as in the anaerobic treatment tank.

The amount of aeration into the aerobic treatment tank is such that the amount of oxygen that decomposes organic matter in raw water into carbon dioxide and water and the amount of oxygen that decomposes sulfur components into sulfate ions are sufficiently supplied. .

When nitrogen-containing organic substances such as amines are used as organic substances to be added to the DMSO-containing wastewater, it is necessary to consider the amount of oxygen required for nitrification.

When the odor gas containing the odor component from the first anaerobic treatment tank is blown into the aerobic treatment tank to carry out the biological deodorization, attention should be paid to the position where the odor gas is blown, and the odor gas is sufficiently reduced to sludge. You need to take care of contact.

The exhaust gas from the aerobic treatment tank is passed through the pipe 15 to the biological deodorizer 4 to completely remove the odor components in the gas. The gas from which the odor component has been completely removed by the biological deodorizing device 4 is discharged from the pipe 16 to the outside of the system.

The treated water in the aerobic treatment tank 2 is then supplied to the pipe 1
7 to the settling tank 3 for solid-liquid separation. The sludge separated in the sludge tank 3 is extracted through the pipe 18 and returned as sludge from the pipe 18a to the anaerobic treatment tank 1 through the pipe 18b.
Each is returned to the more aerobic treatment tank 2. This returned sludge is separated and returned to the anaerobic treatment tank 1 and the aerobic treatment tank 2, and a part of the sludge returned to the anaerobic treatment tank may be sent to the aerobic treatment tank. .

The supernatant water of the settling tank 3 is discharged out of the system as treated water from a pipe 19.

The embodiment shown in FIG. 1 is an embodiment of the present invention, and the present invention is not limited to the illustrated method.

For example, as described above, the aerobic treatment tank can be a plurality of, preferably three or more aerobic treatment tanks connected in series. In this case, in particular, the following structure is adopted. Is preferred.

That is, three or more aeration tanks are connected in series,
The oxygen-containing gas is diffused into the first aeration tank into which the anaerobic treated water flows, and the diffused exhaust gas discharged from each upstream aeration tank connected to the downstream aeration tank is transferred to the next downstream side. To the aeration tank.

With such an aerobic treatment tank configuration, a more reliable decomposition reaction can be carried out by multi-stage aeration treatment of three or more stages, and high-quality treated water can be obtained. Offensive odor components such as DMS and MM contained in the exhaust gas of the tank are diffused into a later-stage aeration tank and processed in the aeration tank so that exhaust gas without odor is obtained from the last-stage aeration tank. become.

Hereinafter, the present invention will be described in more detail with reference to experimental examples, comparative experimental examples, specific examples, and comparative examples.

Experimental Example 1, Comparative Experimental Example 1 Raw water containing 300 mg / l of DMSO in terms of TOC and 200 mg / l of glucose in terms of TOC was anaerobically treated (Experimental Example 1) or aerobic treated tank (Comparative Experimental Example 1). ), The treatment was carried out under the conditions shown in Table 1 below, and the change over time in the DMS concentration in the tank was examined. The results are shown in FIG.

[0039]

[Table 1]

FIG. 3 shows that the biodegradation of DMSO to DMS proceeds well in the coexistence of glucose, but especially under anaerobic conditions (Experimental Example 1), under aerobic conditions (comparative experiment). It is evident that degradation rates as high as about 1.7 times are obtained than in Example 1).

Experimental Example 2, Comparative Experimental Example 2 Raw water containing 50 mg / l of DMS in terms of TOC (Experimental Example 2), and raw water containing 50 mg / l of DMS in terms of TOC and 50 mg / l of glucose in terms of TOC (comparative Regarding Experimental Example 2), aerobic treatment tanks (sludge concentration: 4)
The treatment was performed at 700 mg / l, water temperature: 25 ° C., pH: 7.0), and the time-dependent change in the sulfate ion concentration in the tank was examined. The results are shown in FIG.

FIG. 4 shows that the decomposition from DMS to sulfate ions proceeds well under aerobic conditions. At this time, even if organic substances other than DMS were mixed (Comparative Experimental Example 2), the decomposition rate increased. It is clear that this will not happen.

Example 1 DMSO-containing wastewater was treated according to the method shown in FIG.

D dissolved to 300 mg / l in terms of TOC
To the MSO solution, 200 mg / l of TOC 2-aminoethanol was mixed to adjust the total TOC concentration to 500 mg / l, and the synthetic wastewater whose pH was adjusted to 7 with a phosphate buffer was subjected to 1-liter anaerobic treatment. Water was sequentially passed through a tank and a 2-liter aerobic treatment tank (aeration tank) for treatment. As activated sludge, surplus sludge from an urban sewage treatment plant was used. The load and water temperature of each tank were as shown in Table 2.

Since the present method is a small-sized apparatus, the odor gas in the anaerobic reaction tank in the former stage was not blown into the aerobic reaction tank in the latter stage, but deodorizing treatment was carried out by a biological deodorizer.

As a result, the decomposition reaction of DMSO was observed after 15 days, the residual DMS in the treated water in the aerobic reaction tank was below the lower limit of detection as shown in FIG. 5, and the exhaust gas from the aerobic reaction tank was The DMS concentration therein was also extremely low at 0.1 ppm or less. These results are also shown in Table 2.

Comparative Example 1 An anaerobic treatment tank was not used, and only one 5-liter aerobic treatment tank (aeration tank) was used, and the treatment was carried out at the load and water temperature shown in Table 2. The procedure was as in Example 1.

As a result, as shown in FIG. 5, DMS at 8 to 17 mg / l remained in the treated water, and the DMS concentration in the exhaust gas from the aerobic treatment tank was as high as 15 to 50 ppm. Was intense. These results are also shown in Table 2.

[0049]

[Table 2]

From Table 2, according to the method of the present invention, it is possible to obtain remarkably high quality treated water at a load of 3.3 times that of the conventional aerobic treatment alone. Moreover, it is clear that the odor of the exhaust gas is also greatly reduced.

[0051]

As described above in detail, according to the wastewater treatment method of the present invention, after DMSO is efficiently decomposed into DMS in the anaerobic treatment tank in the presence of other organic substances, This DMS is efficiently decomposed into sulfate ions in the aerobic treatment tank.

[0052] For this reason, the wastewater containing DMSO can be efficiently treated by biological treatment, so that the maintenance and management costs are significantly reduced as compared with general treatment methods such as incineration and oxidation with an oxidizing agent. Can be reduced. The load per treatment tank can be increased as compared with the ordinary activated sludge treatment method. Further, generation of odor is also reduced. Thus, the DMSO-containing wastewater can be efficiently treated at low cost, and high-quality treated water can be obtained.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of a method for treating wastewater containing DMSO of the present invention.

FIG. 2 is an explanatory diagram showing a biodegradation metabolic pathway of DMSO.

FIG. 3 is a graph showing the progress of the decomposition reaction from DMSO to DMS obtained in Experimental Example 1 and Comparative Experimental Example 1.

FIG. 4 is a graph showing the progress of the decomposition reaction of DMS to sulfate ions obtained in Experimental Example 2 and Comparative Experimental Example 2.

FIG. 5 is a graph showing the change over time of the DMS concentration in the treated water obtained by the treatment in Example 1 and Comparative Example 1.

[Explanation of symbols]

 Reference Signs List 1 anaerobic treatment tank 2 aerobic treatment tank 3 sedimentation tank 4 biological deodorizer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C02F 3/30

Claims (1)

(57) [Claims] 1. An aerobic treatment tank in which effluent containing dimethyl sulfoxide is mixed with effluent containing organic matter other than dimethyl sulfoxide, and the mixed effluent is subjected to anaerobic treatment in an anaerobic treatment tank and then aerated. Aerobic treatment, followed by solid-liquid separation treatment to obtain treated water, wherein at least a part of the sludge separated by the solid-liquid separation treatment is returned sludge as the anaerobic treatment tank and the aerobic treatment. A method for treating wastewater containing dimethyl sulfoxide, which is returned to a tank.